单项选择题
A.which
B.where
C.when
D.how
单项选择题 The port clearance for a ship should be granted（）the completion of loading or discharging in the port.
单项选择题 The load chart of a ship crane enables the operator to combine the load radius with boom length to determine the（）.
单项选择题 The boom indicator tells the operator at what angle the boom is compared to the（）.